1,000×
The mcg/mg gap
A milligram is a thousand micrograms. Reading the wrong unit is the error that produces a tenfold dose, and it is the most common one.
Reconstitution and dosing
The exact line to draw to.Not just a number.
Enter your vial, your water and your dose. The syringe fills to the mark you need, and all four steps of the arithmetic sit underneath it.
- Eight compounds preset
- BPC-157, TB-500, retatrutide, tirzepatide and more
- Your numbers stay in the browser
- No account, no upload, and nothing you enter is sent anywhere
- Every step shown
- The working is on the page, not hidden behind the answer
Free · no signupU-100, 50 and 30 unit syringesmcg and mg both handledWorks offline once loaded
Why this exists
The maths is simple.Getting it wrong is not.
- Every protocol is written in mg or mcg. Every syringe is marked in units.
- The conversion depends on how much water you happened to add.
- Change the water volume and every number moves with it.
- The gap between 7.3 units and 73 units is one decimal place.
Four numbers worth knowing before you draw
2 units
The measurement floor
Under two units, the space between graduations is a large share of the dose itself. Small reading errors become large dosing errors.
0.1 ml
Is ten units
A U-100 syringe is marked in units, not millilitres. Every protocol written in mg has to cross that gap before it reaches the barrel.
28 days
After you add water
Bacteriostatic water buys roughly four weeks refrigerated. Sterile water buys far less. The mix date is the thing nobody writes down.
The difference
Stop doing this in your head
The arithmetic is not hard. Doing it from memory, at night, holding a vial, is where it goes wrong.
The usual way
- Guess a water volume
- Do the maths in your head
- Convert mg to units, somehow
- Squint at the barrel
- Hope it was right
With the calculator
- Enter the vial and your dose
- Compare water volumes
- Pick one that lands on a whole mark
- Read the line off the drawing
- Check the working underneath
The tool
Peptide reconstitution calculator
Pick a compound or enter your own numbers. The syringe fills to your mark, and the table underneath shows what a different water volume would give you.
Inputs
mg
ml
Draw to
10units on a 100-unit syringe
Concentration2.5 mg/ml
Volume / dose0.1 ml
Doses / vial20
Lands on 10 units: a whole mark, easy to draw accurately.
Pick a water volume that lands on a readable mark
| Water | Concentration | Volume / dose | Units | Doses / vial |
|---|
The working
Four steps.Step two is the dangerous one.
- 01
Concentration
Peptide divided by water. A 5 mg vial with 2 ml is 2.5 mg/ml. The water volume is your choice, it only decides how big the draw is.
- 02
Micrograms to milligrams
Divide by 1,000. A 250 mcg dose is 0.25 mg. Getting this backwards is a tenfold dosing error.
- 03
Injection volume
Dose divided by concentration. 0.25 mg at 2.5 mg/ml is 0.1 ml.
- 04
Syringe units
On a U-100 syringe, 1 ml is 100 units. So 0.1 ml is the tenth mark.
Bacteriostatic water
There is no correct volume.Only a readable one.
- More water, lower concentration, larger draw, easier to measure.
- Less water, higher concentration, smaller draw, easier to misread.
- Aim for a whole mark. Ten units is far safer to draw than 7.3.
- Stay above two units. Below that the graduations swallow the dose.
Storage
Once it is mixed,the clock starts.
- Bacteriostatic water
- Preserved, so roughly 28 days refrigerated.
- Sterile water
- No preservative. A much shorter window, and not for multi-dose vials.
- Refrigerate, never freeze
- Freezing damages peptides. Keep them cold and out of light.
- Write the date on the vial
- Everything else can be recalculated. A forgotten mix date cannot.
Common questions
How do you calculate peptide dosage in syringe units?
Divide the peptide in the vial (mg) by the bacteriostatic water you added (ml) to get the concentration in mg/ml. Divide your dose by that concentration to get the volume in millilitres. On a U-100 insulin syringe, 1 ml is 100 units, so multiply the volume by 100. A 5 mg vial reconstituted with 2 ml gives 2.5 mg/ml; a 250 mcg dose is 0.1 ml, which is 10 units.
How much bacteriostatic water should I add to a peptide vial?
There is no single correct amount, the water volume only sets the concentration. Choose the volume that makes your dose land on a readable syringe mark. More water means a larger, easier-to-measure draw; less water means a smaller draw. Most vials comfortably hold 2 to 3 ml.
What is the difference between mcg and mg in peptide dosing?
One milligram equals 1,000 micrograms. Confusing the two is the most common and most dangerous error in peptide dosing, because it produces a tenfold overdose or underdose. Always confirm which unit your protocol is written in before drawing.
Why should a dose be at least 2 units on the syringe?
Below about 2 units, the graduation spacing on a standard insulin syringe becomes a large share of the dose itself, so small reading errors translate into large dosing errors. If your dose lands under 2 units, reconstitute with less water so the draw sits on a clearer mark.
How long does a reconstituted peptide vial last?
Once water is added the clock starts. Bacteriostatic water contains a preservative and typically allows around 28 days refrigerated; sterile water has no preservative and a much shorter window. Store reconstituted vials in the refrigerator, never frozen, and note the date you mixed them.
Is this calculator medical advice?
No. It performs arithmetic on numbers you enter and shows every step of the working. It does not know your protocol and will never suggest a dose. Deciding what to take is a matter for you and a qualified prescriber.
Read this before you draw
This tool does arithmetic. It does not know your protocol, and it will never tell you what dose to take.
It converts, it doesn’t prescribe
Every number comes from figures you entered. Deciding the dose is between you and a qualified prescriber.
Check the unit twice
Micrograms and milligrams differ by a factor of 1,000. Read the working and confirm it matches what you intended.
Many of these are not approved medicines
Research peptides are sold without approval, without quality control, and often without accurate labelling. Accurate arithmetic on an unverified vial is still arithmetic on an unverified vial.